Java client hangs when executing a SPARQL select query

Support Bug
1

Hi,

Every once in a while the Java Stardog client is hanging on select queries. After 5 minutes it still hasn't recovered.

After debugging, I think the problem is a timeout in httpclient that is set to 0.

Screen Shot 2017-03-13 at 13.00.27.png3360×2100 993 KB

2

Server status:

bash-4.3# ./stardog-admin server status
Backup Storage Directory : .backup
CPU Load                 : 0.0000 %
Connection Timeout       : 1h
Export Storage Directory : .exports
Memory Heap              : 140M (Allocated: 338M Max: 910M)
Memory Non-Heap          : 108M (Allocated: 111M Max: 1.0G)
Platform Arch            : amd64
Platform OS              : Linux 4.9.12-moby, Java 1.8.0_111-internal
Query All Graphs         : false
Query Timeout            : 5m
Stardog Home             : /home/stardog/data
Stardog Version          : 4.2.3
Strict Parsing           : true
Uptime                   : 25 minutes 50 seconds
Watchdog Enabled         : true
Watchdog Port            : 5833
Watchdog Remote Access   : true
Databases                : 
+------------+------------+-------------+-----------------+----------------------+-----------+
|    Name    | Conn. Open | Trans. Open | Running Queries | Query Avg. Time (ms) | Query/sec |
+------------+------------+-------------+-----------------+----------------------+-----------+
| testSesame |          0 |           0 |               0 |                  0.0 |       0.0 |
+------------+------------+-------------+-----------------+----------------------+-----------+
3

Seems like I may have been forgetting to close my streams. I’m using Iterations.stream and thought that that would close my stream when it was completed, but it doesn’t.

4

Rewriting my code to close my streams has solved this issue.

SelectQuery query = connection
    .select("select ?dato where {?a <" + Arkiv.publisertDato + "> ?dato} limit 1")
    .parameter("a", repository.getIdAsResource());

try (Stream<BindingSet> stream = Iterations.stream(query.execute())) {
    return stream
                 .map(next -> DateTime.parse(next.getBinding("dato").getValue().stringValue()))
                 .findAny();
}
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